A better understanding of the visual character of languages is important in developing our ability to exploit the human visual system. I briefly outline Goodman's distinction between notational and analog languages, and describe its use in developing the notion of syntactic and semantic density as the defining characteristic of visual languages. Several languages are evaluated for their use of density. I conclude that practical languages are most visually effective when their layout is constrained by an important semantic domain. 1. Introduction. Visual programming has a credibility problem. As in user interface design, hypertext, and artificial intelligence, solid work in visual programming is often drowned in the ballyhoo of extravagant claims. And as is also true in the other areas, workers in visual programming are not completely without fault. We are generally quite ready to claim, as does Shu: Pictures are more powerful than words as a means of communication. They can convey mor...

Software metrics have been investigated for the assessment of programs written in a functional programming language. The external attribute of programs considered in this thesis is their comprehensibility to novice programmers. This attribute has been operationalized in a number of experiments. The internal attribute of software which is examined is the structure. Two models for the structure of software have been employed: callgraphs and flowgraphs. The proposed control-flow model captures the operational semantics of function definitions. The objective measurement of the attributes has been supported by tools. The validation of structure metrics has been addressed in certain experiments for programming-in-the-small. The structure of type expressions in functional programs has been analysed in a case study. A simple framework for software metrication proved to be useful. The validation of metrics has been linked with axioms from the representational measurement theory. The control-flow model for functional programs showed its value in the set-up of an

Abstract. The rise of interest in declarative languages for process modeling both justifies and demands empirical investigations into their presumed advantages over more traditional, imperative alternatives. Our concern in this paper is with the ease of maintaining business process models, for example due to changing performance or conformance demands. We aim to contribute to a rigorous, theoretical discussion of this topic by drawing a link to well-established research on maintainability of information artifacts.